pt-table-checksum failes with columns containing Umlaute (ä,ö,ü)

pt-table-checksum failes with columns containing Umlaute (ä,ö,ü), with the following error:
Error checksumming table examvslide.slide: Error executing checksum query: DBD::mysql::st execute failed: Unknown column ‘vergr?sserung’ in ‘field list’ [for Statement “REPLACE INTO monitoring.checksums (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*) AS cnt, COALESCE(LOWER(CONV(BIT_XOR(CAST(CRC32(CONCAT_WS(’#’, schnittname, code, vergr?sserung, massstab, organ, diagnose, themenblock, pr?fung, f?rbung, code2, massstab2, vergr?sserung2, f?rbung2, code3, massstab3, vergr?sserung3, f?rbung3)) AS UNSIGNED)), 10, 16)), 0) AS crc FROM examvslide.slide /checksum table/” with ParamValues: 0=‘examvslide’, 1=‘slide’, 2=1, 3=undef, 4=undef, 5=undef] at ./bin/pt-table-checksum line 10459

Anyone knows how to fix it or is it a bug?
Thanks

I have no idea, but I’m wondering if setting the default character set in your connection to something like utf8 might help? See the DSN options in the pt-table-checksum documentation.

where are DSN options ,can anyone help me ??